Ricin

(BAN, USAN, rINN)

Chemical information

Ricino.

CAS — 9009-86-3.

NOTE. The title ricin is used for the castor seed in Chin. and Fr.

Profile

Ricin is a lectin present in castor seeds, the seeds of Ricinus communis (Euphorbiaceae). It is extremely toxic when given parenterally and the fatal dose by injection has been reported to be around 1 microgram/kg. The toxicity of orally ingested beans depends on how thoroughly they are chewed since the hard seed coat prevents absorption. Ingestion of as few as 3 castor seeds by a child and 4 by an adult may be fatal. Ricin may also be absorbed through abraded skin. It has potential use in aerosol form as an agent of chemical warfare. Toxic effects may be delayed for several days after exposure by any route. Early symptoms include severe gastrointestinal irritation, haemorrhage, vomiting, and diarrhoea, which may result in circulatory collapse. Abnormal liver function tests and pulmonary oedema have been reported. Ophthalmological disturbances ranging from irritation and conjunctivitis to optic nerve damage may occur; miosis and mydriasis have also been reported. Proteinuria, haematuria, and renal impairment may develop and serum creatinine levels may be raised. In severe cases haemolysis of the red blood cells with subsequent acute renal failure may occur. Fatalities due to multiorgan failure have occurred. If the patient presents within 1 hour of ingestion any seeds may be removed by gastric lavage and activated charcoal given. Treatment thereafter is symptomatic. After expression of the oil from castor seeds, the ricin remaining in the seed cake or ‘pomace’ is destroyed by steam treatment. The detoxified pomace is used as a fertiliser. Ricin conjugated with monoclonal or polyclonal antibodies is being studied in the treatment of cancers; zolimomab aritox is an example of such a conjugate. Some of these conjugates have been investigated for various malignancies, particularly leukaemias and lymphomas. To x i c i t y . A report of ricin toxicity after partial chewing and ingestion of 10 to 15 castor oil seeds,1 and reviews2-4 of ricin toxicity, including its potential as an agent of chemical warfare.